1. Field of the Invention
The present invention relates to a raindrop detector used to automatically operate the wiper by detecting raindrops.
2. Description of the Prior Art
FIG. 4 shows an example of a conventional raindrop detector.
The illustrated raindrop detector (100) consists of a vibration device (101) comprising a piezoelectric or electrostriction element and an amplifier (102) connected to the vibration device (101). The detector is installed on the bonnet of a car body 1, which is not illustrated, so that raindrops on the vehicle can be detected easily.
A vibration plate, which is not illustrated, mounted on the above-mentioned vibration device (101) resonates when raindrops hit the plate and raindrop vibration components are converted into electrical signals, which are amplified by the above-mentioned amplifier (102) and are input to the control circuit (103), which is installed in a separate position from the above-mentioned bonnet through a data line (104).
After the above-mentioned electrical signal is processed by the above-mentioned control circuit (103), the power supplied by turning on a wiper switch, which is not illustrated, is fed to the wiper motor (106) through the drive circuit (105) to operate the wiper motor (106) at the intermittent period corresponding to the above-mentioned electrical signal.
By this operation, a wiper blade coupled to the wiper motor (106), but not illustrated, wipes the wiping surface.
In the above-mentioned conventional raindrop detector (100), the electrical signal output from the amplifier (102) is an electrical signal obtained by amplifying frequency at the time when the vibration plate vibrates owing to the impact of raindrops. The electrical signal amplified by the amplifier (102) is transferred to the control circuit (103) through the data line (104). The signal input to the control circuit (103) is output to the drive circuit (105) after being processed in the control circuit (103), and the wiper motor (106) is so designed as to be driven by the signal processed in the control circuit (103) through the drive circuit (105) and to actuate the wiper blade.
Therefore, there is a problem in that the raindrop detector (100) does not provide good response characteristics because the signal requires a lot of time to arrive in the drive circuit (105) from the amplifier (102) through the data line (1040) and the signal processor means in the control circuit (103). The challenge is to solve the aforementioned problem.